1. Field of the Invention
The present invention relates to an apparatus for controlling an operation of a display data channel(DDC) of a monitor so that a personal computer (PC) with DDC function is compatible with a personal computer without DDC function and a method thereof.
2. Description of the Prior Art
FIG. 1 shows a scheme of an integrated circuit(IC) performing DDC function.
If power is applied to a monitor, data of the monitor is successively transmitted to a PC (not shown) connected thereto through a data port SDA of the IC 1 by one byte. In this time, a clock port SCL of the IC is in logic "high" and a vertical synchronization signal is applied from the PC to a port VCLK of IC 1. On the other hand, if the logic state of the clock port SCL is converted from logic "high" to logic "low", an operation mode of the IC 1 is changed. In the changed operation mode, the IC 1 receives a read signal of I.sup.2 C type at the ports SCL and SDA from the PC and on receiving the read signal, data of the monitor is transmitted to the PC synchronized with a clock of the port SCL.
In case a monitor with DDC function, however, is connected to the PC without DDC function, data of the monitor with DDC function is not detected by the PC without DDC function. That is, in using the monitor with DDC function, the PC with DDC function is not compatible with the PC without DDC.